1. Field of the Invention
The present invention concerns an intraluminal prosthesis for a ramification of vessels in the human or animal body. It also relates to a tubular trunk element to be used in such an intraluminal prosthesis and to the method for producing such a tubular trunk element.
2. State of the Art
It has long been attempted to remedy various forms of deterioration which become manifest in the walls of the vessels in the human or animal body, such as the blood vessels, the canals of the gastrointestinal system, the urinary canals, and others. An example of a very common form of deterioration of the type in question involves aneurysms of the blood vessels, in particular aneurysms which affect the infrarenal segments of the abdominal aorta. There, the aorta undergoes dilation, leading to the risk of rupture of the vessel wall and the death of the patient.
Intraluminal prostheses have been used in an attempt to support the defective vessel walls. Various types of intraluminal prostheses with this purpose are described in the literature, and in particular in Patents U.S. Pat No. 4,140,126 and 4,512,332, and in International Patent Applications PCT WO 94/01056 and WO 96/07371. Mention may also be made of PARODI J. C. et al, Transfemoral Intraluminal Graft Implantation for Abdominal Aortic Aneurysms, Annals of Vascular Surgery, Vol. 5, No. 6, 1991, p. 491-499.
These documents describe fixing an intraluminal prosthesis to the distal and proximal necks of the aneurysm, for example an abdominal aortic aneurysm, that is to say to those parts which are the least affected at the onset of the condition. The proximal neck is situated below the renal arteries, and the distal neck is situated just above the aorto-iliac bifurcation. However, no solution is proposed when the aneurysm extends into the branches of this ramification. During the exponential growth of the aneurysm, the necks do in fact also become the site of dilation, particularly the distal neck, and then the iliac arteries. In cases such as this, which are very common, the solutions proposed hereinabove are inadequate.
Attempts have therefore been made to provide intraluminal prostheses for ramifications.
For example, bifurcated intraluminal prostheses are known which have the general appearance of trousers, having, at the three ends, a fastening stent element to be fixed to the proximal neck of the aneurysm and in healthy segments of the iliac arteries (see EP-A-0461791 and EP-A-0539237; T. CHUTER, Bifurcated endovascular graft insertion for abdominal aortic aneurysm, in xe2x80x9cVascular and Endovascular Surgical Techniquesxe2x80x9d, 3rd ed., Ed. RM Greenhalg Publication WD Saunders Company, 1994, p. 92-99). These intraluminal prostheses have the disadvantage of being difficult to place, after aortic release, for introducing each of the legs of the intraluminal prosthesis into their iliac artery. It is generally necessary to use devices for recovery of a femoral cruciate catheter, which demands a high degree of skill on the part of the surgeon.
Other known bifurcated intraluminal prostheses comprise an aortic segment which is continued via an iliac segment. A branch stump measuring 5 mm in diameter protrudes laterally and has to be placed opposite the mouth of the iliac artery not yet provided with its intraluminal prosthesis. It is then necessary to introduce, via this iliac artery, an additional tube which is to be inserted into this small tubular stump. This necessitates a precise positioning of the latter, which is attempted by arranging radiopaque markers on the intraluminal prosthesis (see BLUM U. et al, Abdominal Aortic Aneurysms . . . , International Radiology, Vol. 198, Jan. 1, 1996, p. 25-31). Just as in the above solution, the surgeon needs to be highly skilful to introduce the additional tube into the tubular stump intended for it, and he must have great expertise in the use of intraluminal catheters.
All these embodiments, whether bifurcated with one trunk and two complete legs, or with one trunk, one complete leg and one leg to be inserted in situ into a stump, have the disadvantage of a complicated design. In addition, they are generally supported in a rigid manner by fastening stent elements, uniquely at the proximal neck and in the iliac arteries, hence the danger of too pronounced a bend in one of the two legs at the site of the bifurcation.
In attempting to overcome this latter disadvantage, expandable and retractable stents have been provided which can support a covering, itself also expandable, along the entire length of the bifurcated intraluminal prosthesis. A model of a bifurcated stent, expandable by balloon, has been provided in U.S. Pat. No. 4,994,071, for example. It is clear, however, that the production of a bifurcated intraluminal prosthesis equipped with a complete bifurcated stent is complex and costly. Its introduction into the patient""s body is certainly not easy either.
Finally, intraluminal prostheses are known which are formed by two tubular elements which are to be introduced simultaneously into the aneurysm, the first via one iliac artery, the second via the other iliac artery. The ends of these tubular elements, when they have reached the proximal neck of the aneurysm, are dilated radially in order to be fastened thereto simultaneously, whilst the opposite end of each of these elements is fastened in a similar manner in its corresponding iliac artery. According to one embodiment, a metal stent is dilated in the neck, prior to these operations, so as to receive the two dilatable ends of the aforementioned tubular elements (see EP-A-0551179).
These embodiments have the major disadvantage of not guaranteeing a perfect sealing of the two proximal ends of the tubular elements inside the proximal neck of the aneurysm. This inevitably results in leaks at the periphery of the tubular elements, penetration of blood into the aneurysm and the reestablishment, which is to be avoided, of the blood pressure at this site.
The object of the present invention is to overcome the problems faced and to provide an intraluminal prosthesis for a ramification of vessels in the human or animal body which is applicable to the majority of the anatomical conditions and which is easy to position without having special experience of catheterization. After it has been put into place, this intraluminal prosthesis cannot present any phenomenon of leakage of blood into the cavity of the aneurysm. Moreover, this intraluminal prosthesis will advantageously be very easy to produce and to store.
This problem is resolved by means of an intraluminal prosthesis for a ramification of vessels in the human or animal body, comprising:
a tubular trunk element which is radially expandable and compressible and which is to be applied in the expansion position in a principal vessel of the said ramification, this tubular trunk element axially having two ends and a cavity which is open at these two ends, and
at least one tubular branch element which is radially expandable and compressible and which axially has two ends and a cavity open at these two ends, each branch element being, in its compression position, independent of the tubular trunk element,
this intraluminal prosthesis being characterized in that the cavity of the trunk element is divided into several axial channels over at least part of its length, and in that each branch element has an end which is to be applied, in the expansion position, within one of the said axial channels of the tubular trunk element, and another end situated outside the tubular trunk element, within a secondary vessel of the said ramification.
This intraluminal prosthesis has the advantage of being made up of independent elements, that is to say elements which are to be introduced successively into the body, and which have an external shape similar to the tubular intraluminal prostheses which are known at present. The trunk element is released between the distal and proximal necks of the aneurysm in a conventional manner, like a non-bifurcated intraluminal prosthesis. Each branch element is then introduced via one end inside the trunk element, while remaining at the other end in its corresponding iliac artery. The division of the internal cavity of the tubular trunk element into two axial channels has the effect of artificially displacing the branch a certain distance from the deteriorated branch. The application of a tubular branch element into each axial channel has the effect of preventing any phenomenon of leakage of blood into the aneurysm.
The axial channels are advantageously provided uniquely on a central part of the axial cavity of the tubular trunk element. As will be seen hereinafter, this embodiment facilitates the introduction of the guide and its introducer, then of its branch element, inside the trunk element which is already in place. Furthermore, the bifurcation obtained by two branch elements, fastened at the centre of the trunk element, softens the curvature of the branch elements, which promotes the flow of the body fluids.
According to one advantageous embodiment, the tubular trunk element comprises, between its ends, a sleeve made of flexible, biocompatible material, which is impermeable to the body fluids passing through the said ramification and which forms the said cavity and its channels, and, at least at each end of the trunk element, a tubular stent element which is radially expandable and compressible and to which the sleeve is fixed. According to an improved embodiment of the invention, the tubular trunk element comprises, between its ends, a sleeve made of flexible, biocompatible material, which is impermeable to the body fluids passing through the said ramification and which forms the said cavity and its channels, and a tubular stent, which is radially expandable and compressible, which surrounds the sleeve and on which the latter is fixed at least at the ends of the tubular trunk element. There is therefore no need to envisage a bifurcated stent. It suffices to use tubular, non-bifurcated stents which are easy to make and which have long been known in the art. Such stents are, for example, self-expandable, or expandable by balloon, and examples which may be cited by way of reference are U.S. Pat. Nos. 4,733,655, 4,739,762, 4,776,337, 5,019,090, 5,061,275, 5,092,877, 5,171,262, 5,195,984, EP-A-0183372, EP-A-0556850, EP-A-0621015, GB-1205743, WO-83/03752, WO92/06734.
The sleeve can be made of any known biocompatible material which has, for example, already been used in the production of grafts or coverings for intraluminal prosthesis stents. Particular mention may be made of a material produced, for example, as described in U.S. Pat. Nos. 4,475,272, 4,323,525 or EP-A-0603959. This biologically inert material can be Dacron, Teflon, polyurethane, polycarbonate fibres, or similar materials.
Advantageously, the expandable tubular stent will, in the expansion position, have at least one end which widens outwards. It will preferably have a complete internal and/or external covering.
Each branch element is made in the form of an intraluminal prosthesis known per se and suitable for placing inside a secondary vessel of a ramification, for example an iliac artery.
According to one embodiment of the invention, each tubular branch element comprises, between its ends, a sheath made of a flexible, biocompatible material, which is impermeable to the body fluids passing through the said ramification and which forms its abovementioned cavity, and, at least at each end of the tubular branch element, a tubular stent element which is radially expandable and compressible and on which the sheath is fixed.
According to an advantageous embodiment of the invention, each tubular branch element comprises, between its ends, a tubular stent which is radially expandable and compressible and which has an internal and/or external covering made of a biocompatible material which is impermeable to the body fluids. In this case, as may be observed, the intraluminal prosthesis can be supported along its entire length by several tubular stents, one stent for the trunk element and one stent for each branch element, none of these stents being bifurcated.
The present invention also concerns a tubular trunk element to be used in an intraluminal prosthesis for a ramification of vessels in the human or animal body, this tubular trunk element being radially expandable and compressible and, in the expansion position, being applied in a principal vessel of the said ramification, the tubular trunk element axially having two ends and a cavity which is open at these two ends and which is divided into several axial channels over at least part of its length.
The invention also relates to methods for producing the tubular trunk element according to the invention which is to be used in an intraluminal prosthesis for a ramification of vessels in the human or animal body.
Forms or embodiments of the invention are indicated in the claims which follow.
Other details and features of the invention will be evident from the description which is given hereinafter by way of non-limiting example and with reference to the attached drawings.